<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
    "http://www.w3.org/TR/html4/loose.dtd">
<html>
  <head>
    <title>Page with slow loading iFrames</title>
  </head>
  <body>
    <!-- Takes 3 seconds to load -->
    <iframe src="/common/sleep?time=3"></iframe>

    <!-- Important: do not add a src attribute! -->
    <iframe id="noSrc"></iframe>
  </body>
</html>